package Test01;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 28463
 * Date: 2022—07—04
 * Time: 17:57
 */
public class MyLinkedList {

        static class ListNode {
            public int val;
            public ListNode prev;
            public ListNode next;

            public ListNode(int val) {
                this.val = val;
            }
        }
        public ListNode head;
        public ListNode last;//表示当前链表的尾节点

        //链表打印
        public void display() {
            ListNode cur = head;
            while (cur != null) {
                System.out.print(cur.val + " ");
                cur = cur.next;
            }
            System.out.println();
        }

        //头插法
        public void addFirst(int data) {
            ListNode node = new ListNode(data);
            if (head == null) {
                head = node;
                last = node;
            } else {
                node.next = head;
                head.prev = node;
                head = node;
            }
        }

        //尾插法
        public void addLast(int data) {
            ListNode node = new ListNode(data);
            if (head == null) {
                head = node;
                last = node;
            } else {
                node.prev = last;
                last.next = node;
                last = last.next;
            }
        }
        //先找到index下标节点
        private ListNode findIndex(int index) {
            ListNode cur = head;
            while(index != 0) {
                cur = cur.next;
                index--;
            }
            return cur;
        }
        //任意位置插入,第一个数据节点为0号下标
        public void addIndex(int index, int data) {
            //1.检查index合法性
            if (index < 0 || index > size()) {
                throw new IndexNotlegalException("双向链表index不合法");
            }
            if (index == 0) {
                addFirst(data);
                return;
            }
            if (index ==size()) {
                addLast(data);
                return;
            }
            ListNode node = new ListNode(data);
            //2.获取当前的index位置的结点地址
            ListNode cur = findIndex(index);
            node.next = cur;
            cur.prev.next = node;
            node.prev = cur.prev;
            cur.prev = node;
        }


        //查找是否包含关键字key是否在链表当中
        public boolean contains(int key) {
            ListNode cur = head;
            while (cur != null) {
                if (cur.val == key) {
                    return true;
                }
                cur = cur.next;
            }
            return true;
        }

        //删除第一次出现关键字为key的节点
        public void remove(int key) {
            ListNode cur = head;
            while (cur != null) {
                //找到了删除
                if (cur.val == key) {
                    if (cur == head) {
                        //1.删除头部
                        head = head.next;
                        if (head != null) {
                            //防止只有一个节点
                            head.prev = null;
                        }
                    } else {
                        cur.prev.next = cur.next;
                        if (cur.next != null) {
                            //2.删除中间结点
                            cur.next.prev = cur.prev;
                        } else {
                            //3，删除尾部
                            last = cur.prev;
                        }
                    }
                    return;
                }
                cur = cur.next;
            }
        }

        //删除所有值为key的节点
        public void removeAllKey(int key) {
            ListNode cur = head;
            while (cur != null) {
                //找到了删除
                if (cur.val == key) {
                    if (cur == head) {
                        //1.删除头部
                        head = head.next;
                        if (head != null) {
                            //防止只有一个节点
                            head.prev = null;
                        }
                    } else {
                        cur.prev.next = cur.next;
                        if (cur.next != null) {
                            //2.删除中间结点
                            cur.next.prev = cur.prev;
                        } else {
                            //3，删除尾部
                            last = cur.prev;
                        }
                    }
                }
                cur = cur.next;
            }
        }
        //删除链表中所有结点
        public void clear() {
            head = null;
            last = null;
        }
        //求链表长度
        public int size() {
            int count = 0;
            ListNode cur = head;
            while(cur != null) {
               count++;
               cur = cur.next;
            }
            return count;
        }
}

